Tropical and Boreal Forest – Atmosphere Interactions: A Review

Paulo Artaxo; Hans-Christen Hansson; Meinrat O. Andreae; Jaana Bäck; Eliane Gomes Alves; Henrique M. J. Barbosa; Frida Bender; Efstratios Bourtsoukidis; Samara Carbone; Jinshu Chi; Stefano Decesari; Viviane R. Després; Florian Ditas; Ekaterina Ezhova; Sandro Fuzzi; Niles J. Hasselquist; Jost Heintzenberg; Bruna A. Holanda; Alex Guenther; Hannele Hakola; Liine Heikkinen; Veli-Matti Kerminen; Jenni Kontkanen; Radovan Krejci; Markku Kulmala; Jost V. Lavric; Gerrit de Leeuw; Katrianne Lehtipalo; Luiz Augusto T. Machado; Gordon McFiggans; arco Aurelio M. Franco; Bruno Backes Meller; Fernando G. Morais; Claudia Mohr; William Morgan; Mats B. Nilsson; Matthias Peichl; Tuukka Petäjä; Maria Praß; Christopher Pöhlker; Mira L. Pöhlker; Ulrich Pöschl; Celso Von Randow; Ilona Riipinen; Janne Rinne; Luciana V. Rizzo; Daniel Rosenfeld; Maria A. F. Silva Dias; Larisa Sogacheva; Philip Stier; Erik Swietlicki; Matthias Sörgel; Peter Tunved; Aki Virkkula; Jian Wang; Bettina Weber; Ana Maria Yáñez-Serrano; Paul Zieger; Eugene Mikhailov; James N. Smith; Jürgen Kesselmeier
2022 | TELLUS B | 74 (24-163)

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments.

The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction.

Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink.

It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.

Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS

Siegel, K.; Karlsson, L.; Zieger, P.; Baccarini, A.; Schmale, J.; Lawler, M.; Salter, M.; Leck, C.; Ekman, A.; Riipinen, I.; Mohr, C.
2021 | Environ. Sci. Atmos. | 1 (4) (161-175)

The remote central Arctic during summertime has a pristine atmosphere with very low aerosol particle concentrations. As the region becomes increasingly ice-free during summer, enhanced ocean-atmosphere fluxes of aerosol particles and precursor gases may therefore have impacts on the climate. However, large knowledge gaps remain regarding the sources and physicochemical properties of aerosols in this region. Here, we present insights into the molecular composition of semi-volatile aerosol components collected in September 2018 during the MOCCHA (Microbiology-Ocean-Cloud-Coupling in the High Arctic) campaign as part of the Arctic Ocean 2018 expedition with the Swedish Icebreaker Oden. Analysis was performed offline in the laboratory using an iodide High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). Our analysis revealed significant signal from organic and sulfur-containing compounds, indicative of marine aerosol sources, with a wide range of carbon numbers and O : C ratios. Several of the sulfur-containing compounds are oxidation products of dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae. Comparison of the time series of particulate and gas-phase DMS oxidation products did not reveal a significant correlation, indicative of the different lifetimes of precursor and oxidation products in the different phases. This is the first time the FIGAERO-HRToF-CIMS was used to investigate the composition of aerosols in the central Arctic. The detailed information on the molecular composition of Arctic aerosols presented here can be used for the assessment of aerosol solubility and volatility, which is relevant for understanding aerosol–cloud interactions.

Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition

Wu, C; Bell, DM; Graham, EL; Haslett, S; Riipinen, I; Baltensperger, U; Bertrand, A; Giannoukos, S; Schoonbaert, J; El Haddad, I; Prevot, ASH; Huang, W; Mohr, C
2021 | Atmos. Chem. Phys. | 21 (19) (14907-14925)
alpha-pinene , carbonyl nitrates , chemical composition , evaporation kinetics , isoprene oxidation , mass-spectrometer , model , no3 , optical-properties , photolysis

Night-time reactions of biogenic volatile organic compounds (BVOCs) and nitrate radicals (NO3) can lead to the formation of NO3-initiated biogenic secondary organic aerosol (BSOANO(3)). Here, we study the impacts of light exposure on the chemical composition and volatility of BSOANO(3) formed in the dark from three precursors (isoprene, alpha-pinene, and beta-caryophyllene) in atmospheric simulation chamber experiments. Our study represents BSOANO(3) formation conditions where reactions between peroxy radicals (RO2 + RO2) and between RO2 and NO3 are favoured. The emphasis here is on the identification of particle-phase organonitrates (ONs) formed in the dark and their changes during photolytic ageing on timescales of similar to 1 h. The chemical composition of particle-phase compounds was measured with a chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Volatility information on BSOANO(3) was derived from FIGAERO-CIMS desorption profiles (thermograms) and a volatility tandem differential mobility analyser (VTDMA). During photolytic ageing, there was a relatively small change in mass due to evaporation (< 5 % for the isoprene and alpha-pinene BSOANO3, and 12 % for the beta-caryophyllene BSOANO(3)), but we observed significant changes in the chemical composition of the BSOANO(3). Overall, 48 %, 44 %, and 60 % of the respective total signal for the isoprene, alpha-pinene, and beta-caryophyllene BSOANO(3) was sensitive to photolytic ageing and exhibited decay. The photolabile compounds include both monomers and oligomers. Oligomers can decompose into their monomer units through photolysis of the bonds (e.g. likely O-O) between them. Fragmentation of both oligomers and monomers also happened at other positions, causing the formation of compounds with shorter carbon skeletons. The cleavage of the nitrate functional group from the carbon chain was likely not a main degradation pathway in our experiments. In addition, photolytic degradation of compounds changes their volatility and can lead to evaporation. We use different methods to assess bulk volatilities and discuss their changes during both dark ageing and photolysis in the context of the chemical changes that we observed. We also reveal large uncertainties in saturation vapour pressure estimated from parameterizations for the ON oligomers with multiple nitrate groups. Overall, our results suggest that photolysis causes photodegradation of a substantial fraction of BSOANO(3), changes both the chemical composition and the bulk volatility of the particles, and might be a potentially important loss pathway of BSOANO(3) during the night-to-day transition.

Steady-State Mass Balance Model for Predicting Particle-Gas Concentration Ratios of PBDEs

2021 | Environ. Sci. Technol. | 55 (14) (9425-9433)
air partition-coefficients , aromatic-hydrocarbons pahs , brominated flame retardants , dibenzo-p-dioxins , diphenyl ethers pbdes , equilibration time scales , global air , long range transport , semivolatile organic-chemicals , vapor-pressure
Assuming equilibrium partitioning between the gas and particle phases has been shown to overestimate the fraction of low-volatility chemicals in the particle phase. Here, we present a new steady-state mass balance model that includes separate compartments for fine and coarse aerosols and the gas phase and study its sensitivity to the input parameters. We apply the new model to investigate deviations from equilibrium partitioning by exploring model scenarios for seven generic aerosol scenarios representing different environments and different distributions of emissions as the gas phase, fine aerosol, and coarse aerosol. With 100% of emissions as the particle phase, the particle-gas concentration ratio in our model is similar to the equilibrium model, while differences are up to a factor of 10(6) with 100% of emissions as the gas phase. The particle-gas concentration ratios also depend on the particle size distributions and aerosol loadings in the different environmental scenarios. The new mass balance model can predict the particle-gas concentration ratio with more fidelity to measurements than equilibrium models. However, further laboratory-based evaluations and calibrations of the standard sampling techniques, field investigations with preferably size-resolved measurements of aerosol particle composition, together with the appropriate process modeling for low-volatility chemicals are warranted.

Transport and chemistry of isoprene and its oxidation products in deep convective clouds

Bardakov, R; Thornton, JA; Riipinen, I; Krejci, R; Ekman, AML
2021 | Tellus Ser. B-Chem. Phys. Meteorol. | 73 (1)
convective transport of isoprene , deep convective cloud trajectories , epoxide formation , gas-phase , ice , particle formation , photochemical box model , photolysis frequencies , rain forest , secondary organic aerosol , thermodynamic model , tropical upper troposphere , united-states
Deep convective clouds can transport trace gases from the planetary boundary layer into the upper troposphere where subsequent chemistry may impact aerosol particle formation and growth. In this modelling study, we investigate processes that affect isoprene and its oxidation products injected into the upper troposphere by an isolated deep convective cloud in the Amazon. We run a photochemical box model with coupled cloud microphysics along hundreds of individual air parcel trajectories sampled from a cloud-resolving model simulation of a convective event. The box model simulates gas-phase chemical reactions, gas scavenging by liquid and ice hydrometeors, and turbulent dilution inside a deep convective cloud. The results illustrate the potential importance of gas uptake to anvil ice in regulating the intensity of the isoprene oxidation and associated low volatility organic vapour concentrations in the outflow. Isoprene transport and fate also depends on the abundance of lightning-generated nitrogen oxide radicals (NOx = NO + NO2). If gas uptake on ice is efficient and lightning activity is low, around 30% of the boundary layer isoprene will survive to the cloud outflow after approximately one hour of transport, while all the low volatile oxidation products will be scavenged by the cloud hydrometeors. If lightning NOx is abundant and gas uptake by ice is inefficient, then all isoprene will be oxidised during transport or in the immediate outflow region, while several low volatility isoprene oxidation products will have elevated concentrations in the cloud outflow. Reducing uncertainties associated with the uptake of vapours on ice hydrometeors, especially HO2 and oxygenated organics, is essential to improve predictions of isoprene and its oxidation products in deep convective outflows and their potential contribution to new particle formation and growth.

The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic – a simulation study supported by observational data

Bulatovic, I; Igel, AL; Leck, C; Heintzenberg, J; Riipinen, I; Ekman, AML
2021 | Atmos. Chem. Phys. | 21 (5) (3871-3897)
The potential importance of Aitken mode particles (diameters similar to 25-80 nm) for stratiform mixed-phase clouds in the summertime high Arctic (> 80 degrees N) has been investigated using two large-eddy simulation models. We find that, in both models, Aitken mode particles significantly affect the simulated microphysical and radiative properties of the cloud and can help sustain the cloud when accumulation mode concentrations are low (< 10-20 cm(-3)), even when the particles have low hygroscopicity (hygroscopicity parameter - kappa = 0.1). However, the influence of the Aitken mode decreases if the overall liquid water content of the cloud is low, either due to a higher ice fraction or due to low radiative cooling rates. An analysis of the simulated supersaturation (ss) statistics shows that the ss frequently reaches 0.5 % and sometimes even exceeds 1 %, which confirms that Aitken mode particles can be activated. The modelling results are in qualitative agreement with observations of the Hoppel minimum obtained from four different expeditions in the high Arctic. Our findings highlight the importance of better understanding Aitken mode particle formation, chemical properties and emissions, particularly in clean environments such as the high Arctic.

Molecular Perspective on Water Vapor Accommodation into Ice and Its Dependence on Temperature

Daniel Schlesinger; Samuel J. Lowe; Tinja Olenius; Xiangrui Kong; Jan B. C. Pettersson; Ilona Riipinen
2020 | JOURNAL OF PHYSICAL CHEMISTRY A | 124 (51) (10879-10889)

Open questions on atmospheric nanoparticle growth

Yli-Juuti, T; Mohr, C; Riipinen, I
Cloud droplets form in the atmosphere on aerosol particles, many of which result from nucleation of vapors. Here the authors comment on current knowledge and open questions regarding the condensational growth of nucleated particles to sizes where they influence cloud formation.

Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results

Petaja, T; Duplissy, EM; Tabakova, K; Schmale, J; Altstadter, B; Ancellet, G; Arshinov, M; Balin, Y; Baltensperger, U; Bange, J; Beamish, A; Belan, B; Berchet, A; Bossi, R; Cairns, WRL; Ebinghaus, R; El Haddad, I; Ferreira-Araujo, B; Franck, A; Huang, L; Hyvarinen, A; Humbert, A; Kalogridis, AC; Konstantinov, P; Lampert, A; MacLeod, M; Magand, O; Mahura, A; Marelle, L; Masloboev, V; Moisseev, D; Moschos, V; Neckel, N; Onishi, T; Osterwalder, S; Ovaska, A; Paasonen, P; Panchenko, M; Pankratov, F; Pernov, JB; Platis, A; Popovicheva, O; Raut, JC; Riandet, A; Sachs, T; Salvatori, R; Salzano, R; Schroder, L; Schon, M; Shevchenko, V; Skov, H; Sonke, JE; Spolaor, A; Stathopoulos, VK; Strahlendorff, M; Thomas, JL; Vitale, V; Vratolis, S; Barbante, C; Chabrillat, S; Dommergue, A; Eleftheriadis, K; Heilimo, J; Law, KS; Massling, A; Noe, SM; Paris, JD; Prevot, ASH; Riipinen, I; Wehner, B; Xie, ZY; Lappalainen, HK
2020 | Atmos. Chem. Phys. | 20 (14) (8551-8592)
The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project "iCUPE - integrative and Comprehensive Understanding on Polar Environments" to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.

Rapid growth of new atmospheric particles by nitric acid and ammonia condensation

Wang, MY; Kong, WM; Marten, R; He, XC; Chen, DX; Pfeifer, J; Heitto, A; Kontkanen, J; Dada, L; Kurten, A; Yli-Juuti, T; Manninen, HE; Amanatidis, S; Amorim, A; Baalbaki, R; Baccarini, A; Bell, DM; Bertozzi, B; Brakling, S; Brilke, S; Murillo, LC; Chiu, R; Chu, BW; De Menezes, LP; Duplissy, J; Finkenzeller, H; Carracedo, LG; Granzin, M; Guida, R; Hansel, A; Hofbauer, V; Krechmer, J; Lehtipalo, K; Lamkaddam, H; Lampimaki, M; Lee, CP; Makhmutov, V; Marie, G; Mathot, S; Mauldin, RL; Mentler, B; Muller, T; Onnela, A; Partoll, E; Petaja, T; Philippov, M; Pospisilova, V; Ranjithkumar, A; Rissanen, M; Rorup, B; Scholz, W; Shen, JL; Simon, M; Sipila, M; Steiner, G; Stolzenburg, D; Tham, YJ; Tome, A; Wagner, AC; Wang, DYS; Wang, YH; Weber, SK; Winkler, PM; Wlasits, PJ; Wu, YH; Xiao, M; Ye, Q; Zauner-Wieczorek, M; Zhou, XQ; Volkamer, R; Riipinen, I; Dommen, J; Curtius, J; Baltensperger, U; Kulmala, M; Worsnop, DR; Kirkby, J; Seinfeld, JH; El-Haddad, I; Flagan, RC; Donahue, NM
2020 | Nature | 581 (7807) (184-+)
A list of authors and their affiliations appears at the end of the paper New-particle formation is a major contributor to urban smog(1,2), but how it occurs in cities is often puzzling(3). If the growth rates of urban particles are similar to those found in cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new urban particles should be rapidly scavenged by the high concentration of pre-existing particles. Here we show, through experiments performed under atmospheric conditions in the CLOUD chamber at CERN, that below about +5 degrees Celsius, nitric acid and ammonia vapours can condense onto freshly nucleated particles as small as a few nanometres in diameter. Moreover, when it is cold enough (below -15 degrees Celsius), nitric acid and ammonia can nucleate directly through an acid-base stabilization mechanism to form ammonium nitrate particles. Given that these vapours are often one thousand times more abundant than sulfuric acid, the resulting particle growth rates can be extremely high, reaching well above 100 nanometres per hour. However, these high growth rates require the gas-particle ammonium nitrate system to be out of equilibrium in order to sustain gas-phase supersaturations. In view of the strong temperature dependence that we measure for the gas-phase supersaturations, we expect such transient conditions to occur in inhomogeneous urban settings, especially in wintertime, driven by vertical mixing and by strong local sources such as traffic. Even though rapid growth from nitric acid and ammonia condensation may last for only a few minutes, it is nonetheless fast enough to shepherd freshly nucleated particles through the smallest size range where they are most vulnerable to scavenging loss, thus greatly increasing their survival probability. We also expect nitric acid and ammonia nucleation and rapid growth to be important in the relatively clean and cold upper free troposphere, where ammonia can be convected from the continental boundary layer and nitric acid is abundant from electrical storms(4,5).

A Novel Framework to Study Trace Gas Transport in Deep Convective Clouds

Bardakov, R; Riipinen, I; Krejci, R; Savre, J; Thornton, JA; Ekman, AML
Deep convective clouds reach the upper troposphere (8-15 km height). In addition to moisture and aerosol particles, they can bring aerosol precursor gases and other reactive trace gases from the planetary boundary layer to the cloud top. In this paper, we present a method to estimate trace gas transport based on the analysis of individual air parcel trajectories. Large eddy simulation of an idealized deep convective cloud was used to provide realistic environmental input to a parcel model. For a buoyant parcel, we found that the trace gas transport approximately follows one out of three scenarios, determined by a combination of the equilibrium vapor pressure (containing information about water-solubility and pure component saturation vapor pressure) and the enthalpy of vaporization. In one extreme, the trace gas will eventually be completely removed by precipitation. In the other extreme, there is almost no vapor condensation on hydrometeors and most of the gas is transported to the top of the cloud. The scenario in between these two extremes is also characterized by strong gas condensation, but a small fraction of the trace gas may still be transported aloft. This approach confirms previously suggested patterns of inert trace gas behavior in deep convective clouds, agrees with observational data, and allows estimating transport in analytically simple and computationally efficient way compared to explicit cloud-resolving model calculations.

Size-dependent influence of NOx on the growth rates of organic aerosol particles

Yan, C; Nie, W; Vogel, AL; Dada, L; Lehtipalo, K; Stolzenburg, D; Wagner, R; Rissanen, MP; Xiao, M; Ahonen, L; Fischer, L; Rose, C; Bianchi, F; Gordon, H; Simon, M; Heinritzi, M; Garmash, O; Roldin, P; Dias, A; Ye, P; Hofbauer, V; Amorim, A; Bauer, PS; Bergen, A; Bernhammer, AK; Breitenlechner, M; Brilke, S; Buchholz, A; Mazon, SB; Canagaratna, MR; Chen, X; Ding, A; Dommen, J; Draper, DC; Duplissy, J; Frege, C; Heyn, C; Guida, R; Hakala, J; Heikkinen, L; Hoyle, CR; Jokinen, T; Kangasluoma, J; Kirkby, J; Kontkanen, J; Kurten, A; Lawler, MJ; Mai, H; Mathot, S; Mauldin, RL; Molteni, U; Nichman, L; Nieminen, T; Nowak, J; Ojdanic, A; Onnela, A; Pajunoja, A; Petaja, T; Piel, F; Quelever, LLJ; Sarnela, N; Schallhart, S; Sengupta, K; Sipila, M; Tome, A; Trostl, J; Vaisanen, O; Wagner, AC; Ylisirnio, A; Zha, Q; Baltensperger, U; Carslaw, KS; Curtius, J; Flagan, RC; Hansel, A; Riipinen, I; Smith, JN; Virtanen, A; Winkler, PM; Donahue, NM; Kerminen, VM; Kulmala, M; Ehn, M; Worsnop, DR
2020 | Sci. Adv. | 6 (22)
Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOx) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOx. We show that NOx suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOx. By illustrating how NOx affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOx level in forest regions around the globe.

Contact information

Visiting addresses:

Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Toxicological Chemistry)

Mailing address:
Department of Environmental Science
Stockholm University
106 91 Stockholm

Press enquiries should be directed to:

Stella Papadopoulou
Science Communicator
Phone +46 (0)8 674 70 11